Pompe disease (also known as glycogen storage disease type II; acid alpha-glucosidase deficiency; acid maltase deficiency; GAA deficiency; GSD II; glycogenosis type II; glycogenosis, generalized, cardiac form; cardiomegalia glycogenica diffusa; acid maltase deficiency; AMD; or alpha-1,4-glucosidase deficiency) is an autosomal recessive metabolic genetic disorder characterized by mutations in the gene for the lysomsomal enzyme acid alpha-glucosidase (GAA) (also known as acid maltase). Mutations in the GAA gene eliminate or reduce the ability of the GAA enzyme to hydrolyze the α-1,4 and α-1,6 linkages in glycogen, maltose and isomaltose. As a result, glycogen accumulates in the lysosomes and cytoplasm of cells throughout the body leading to cell and tissue destruction. Tissues that are particularly affected include skeletal muscle and cardiac muscle. The accumulated glycogen causes progressive muscle weakness leading to cardiomegaly, ambulatory difficulties and respiratory insufficiency.
Three forms of Pompe disease have been identified, including the classic infantile-onset disease, non-classic infantile-onset disease and late onset disease. The classic infantile-onset form is characterized by muscle weakness, poor muscle tone, hepatomegaly and cardiac defects. The incidence of the disease is approximately 1 in 140,000 individuals. Patients with this form of the disease often die of heart failure in the first year of life. The non-classic infantile-onset form of the disease is characterized by delayed motor skills, progressive muscle weakness and in some instances cardiomegaly. Patients with this form of the disease often live only into early childhood due to respiratory failure. The late-onset form of the disease may present in late childhood, adolescence or adulthood and is characterized by progressive muscle weakness of the legs and trunk.
Currently, there is no cure for Pompe disease and the standard of care is enzyme replacement therapy (ERT) with supportive care for cardiomyopathy and physical therapy for muscle weakness and respiratory symptoms.